{"record":{"id":"9a48505ff694b945","repo":"OrchardCMS/OrchardCore","slug":"couldn-t-generate-a-unique-user-id-too-many-attempts","errorCode":null,"errorMessage":"Couldn't generate a unique user id. Too many attempts.","messagePattern":"Couldn't generate a unique user id\\. Too many attempts\\.","errorType":"exception","errorClass":"ApplicationException","httpStatus":null,"severity":"error","filePath":"src/OrchardCore/OrchardCore.Users.Core/Services/UserStore.cs","lineNumber":95,"sourceCode":"        }\n\n        var newUserId = newUser.UserId;\n\n        if (string.IsNullOrEmpty(newUserId))\n        {\n            // Due to database collation we normalize the userId to lower invariant.\n            newUserId = _userIdGenerator.GenerateUniqueId(user).ToLowerInvariant();\n        }\n\n        try\n        {\n            var attempts = 10;\n\n            while (await _session.QueryIndex<UserIndex>(x => x.UserId == newUserId).CountAsync(cancellationToken) != 0)\n            {\n                if (attempts-- == 0)\n                {\n                    throw new ApplicationException(\"Couldn't generate a unique user id. Too many attempts.\");\n                }\n\n                newUserId = _userIdGenerator.GenerateUniqueId(user).ToLowerInvariant();\n            }\n\n            newUser.UserId = newUserId;\n\n            var context = new UserCreateContext(user);\n\n            await Handlers.InvokeAsync((handler, context) => handler.CreatingAsync(context), context, _logger);\n\n            if (context.Cancel)\n            {\n                return IdentityResult.Failed();\n            }\n\n            await _session.SaveAsync(user, cancellationToken: cancellationToken);\n            await _session.FlushAsync(cancellationToken);","sourceCodeStart":77,"sourceCodeEnd":113,"githubUrl":"https://github.com/OrchardCMS/OrchardCore/blob/4306c0717fe573f6fca1b4955909ddab6a192807/src/OrchardCore/OrchardCore.Users.Core/Services/UserStore.cs#L77-L113","documentation":"Thrown by UserStore.CreateAsync when the IUserIdGenerator fails to produce a unique UserId after 10 collision-check attempts against the UserIndex. Each attempt regenerates an id and re-queries the index; if all 10 collide, the store gives up rather than create a duplicate id. It indicates either a pathologically weak id generator or an index/query problem making every candidate appear taken.","triggerScenarios":"Creating a new user (CreateAsync) while a deterministic UserIdGenerator (e.g. one derived from the username/email) collides with existing users repeatedly; or the UserIndex query erroneously matches everything, so every candidate id appears taken.","commonSituations":"Custom or misconfigured IUserIdGenerator implementations that emit constant or low-entropy ids; large user tables with short/generated ids; broken UserIndex provider returning false positives during user provisioning or setup recipes.","solutions":["Check the registered IUserIdGenerator implementation and ensure it emits high-entropy, unique ids (e.g. Guid-based).","Verify the UserIndex index provider is correctly registered so the uniqueness query is accurate.","Retry user creation once a collision burst has passed; if it persists, inspect the users table for duplicate/stale UserId values.","Wrap CreateAsync in try-catch for ApplicationException and surface a user-friendly provisioning failure."],"exampleFix":"// before\nservices.AddSingleton<IUserIdGenerator, MyFixedPrefixGenerator>();\n// after\nservices.AddScoped<IUserIdGenerator, GuidUserIdGenerator>();","handlingStrategy":"try-catch","validationCode":"var existing = await _session.QueryIndex<UserIndex>(x => x.UserId == candidateId).CountAsync();\nif (existing != 0) { /* regenerate before calling CreateAsync */ }","typeGuard":"bool IsUsableId(string id) => !string.IsNullOrWhiteSpace(id) && id.Length >= 16;","tryCatchPattern":"try { await _userManager.CreateAsync(user); }\ncatch (ApplicationException ex) when (ex.Message.Contains(\"unique user id\"))\n{ _logger.LogError(ex, \"UserId generation exhausted retries\"); return Problem(\"User provisioning failed\"); }","preventionTips":["Use a Guid- or high-entropy-based IUserIdGenerator","Keep the UserIndex provider correctly registered","Load-test user provisioning with large user tables","Never seed users with hand-crafted short ids"],"tags":["users","uniqueness","provisioning"],"backgroundTag":"internal-invariant-violation","analyzedSha":"4306c0717fe573f6fca1b4955909ddab6a192807","analyzedAt":"2026-09-13T17:41:05.024Z","contentChangedAt":"2026-09-13T17:41:05.024Z","schemaVersion":2},"datasetVersion":"2026-09-15T23:17:13.987Z"}